An increasing demand for electronic equipment that is smaller, lighter, and more compact has resulted in a concomitant demand for semiconductor packages that have smaller outlines and mounting areas or “footprints.” One response to this demand has been the development of the ball grid array (BGA) semiconductor package, which “surface mounts” and electronically connects to an associated carrier substrate (e.g., a printed circuit board (PCB)) with a plurality of solder balls. Another response has been the development of the “flip-chip” method of attachment and connection of semiconductor chips or “dice” to substrates (e.g., PCBs or lead-frames). Flip-chip mounting involves the formation of bumped contacts (e.g., solder balls) on the active surface of the die, then inverting or “flipping” the die upside down and reflowing the bumped contacts (i.e., heating the bumped contacts to the melting point) to fuse them to the corresponding pads on the substrate.
In both the flip-chip die and BGA package mounting and connection methods, thermo-mechanical reliability is becoming an increasing concern of the electronic industry. Notably, the board-level reliability of the solder-joints is becoming one of the most critical issues for successful application of such mounting and connection methods.
For example, BGA packages are being used to house integrated circuits that are operating at increasing higher speeds. Heatsinks are being mounted to the BGA package to improve the overall package thermal performance. In some cases, the heatsink is relatively heavy compared to the overall weight of the BGA package. For example, the heatsink may comprise much as 60 percent of the total weight. Such a heatsink will reduce the final solder joint standoff when the package is mounted to a supporting substrate (e.g., PCB). The solder joint standoff is the distance between the substrate and the package. A lower standoff reduces package board level reliability.
Accordingly, there exists a need in the art for a solder ball assembly for a semiconductor device that provides for improved solder joint standoff and package board level reliability.